Devein shrimp and remove the tail, if desired. Trim ends of asparagus.
Preheat oven to 425°F.
Combine all ingredients for the seasoning.
Cut salmon into four or five equal parts.
Arrange salmon and asparagus on a large baking sheet. Season salmon and asparagus (there will be leftover seasoning). Add lemon and butter slices to salmon and on the asparagus. Drizzle with oil. Bake 5 minutes.
Meanwhile, season shrimp and toss to coat.
Add shrimp to baking sheet, spread out evenly. Add leftover butter and lemon over shrimp. Return to oven. Bake another 7-9 minutes, until shrimp and salmon are fully cooked.
Pour the butter juices over the salmon, shrimp and asparagus.